Your article was great in helping me find the replacement files, the only problem is that I cannot replace the originals as it says I do not have permission, even though I am an administrator - examining the File's properties / security, I find that three users are listed, System, myself and an "Account unknown" with a huge number sequence, This unknown user and System has full permissions whereas I have only 'read' and 'read and execute' when I try and edit permissions, they are all shown greyed out, indicating that I am unable to change them If I try and replace, rename etc one of these files, I am told that I need permission from this unknown user (plus huge number sequence) How can I over-ride or delete this unknown user?